In general, artificial breast prostheses are used in reconstructive plastic surgery for a breast when breast loss occurs due to diseases or accidents and in cosmetic surgery for a malformed breast. In terms of anatomy, artificial breast prostheses are also used for the substitution of organs or tissues.
Artificial breast prostheses are products in which a filling material, such as saline, hydro-gel, and silicone gel, is filled in an envelope formed of silicone that is implantable to an organ (hereinafter referred to as a “shell”). These artificial breast prostheses may be classified into round type products and water drop shaped products (anatomical type) according to the shape of a product, and may be classified into smooth products and textured products according to the surface conditions of a product. More particularly, the artificial breast prostheses will be described in brief as follows.
A saline filled artificial breast prosthesis is configured such that saline is injected or is injectable into a shell formed of silicone (more particularly, the shell being formed of polyorganosiloxane). The saline filled artificial breast prosthesis has a structure consisting of a silicone shell and a valve.
Although the saline filled artificial breast prosthesis ensures safety even if the filling material leaks into the human body after rupture of the shell as a result of using sterile saline as the filling material, and is easy to change the volume of a breast by adjusting the injection amount of saline, the saline filled artificial breast prosthesis is significantly deteriorated to the touch after surgery as compared to other artificial breast prostheses and the shell thereof has inferior durability.
A hydro-gel filled artificial breast prosthesis is configured such that hydro-gel composed of monosaccharide and polysaccharides is filled within the shell as in the above-described saline filled artificial breast prosthesis. The hydro-gel filled artificial breast prosthesis was developed based on the principle that the filling material can be absorbed into and excreted from the human body even if the filling material leaks due to rupture of the prosthesis.
A hydro-gel filled artificial breast prosthesis is configured such that hydro-gel composed of monosaccharide and polysaccharides is filled within the shell as in the above-described saline filled artificial breast prosthesis. The hydro-gel filled artificial breast prosthesis was developed based on the principle that the filling material can be absorbed into and excreted from the human body even if the filling material leaks due to rupture of the prosthesis.
However, in the case of the hydro-gel filled artificial breast prosthesis, long-term safety has not been established, volume change over time and occurrence of wrinkles may increase after the artificial breast prosthesis is implanted, and feeling is unnatural as compared to a silicone artificial breast prosthesis. Accordingly, the hydro-gel filled artificial breast prosthesis has not been distributed in the market since 2000 as safety thereof has yet to be proven.
A silicone gel filled artificial breast prosthesis is configured such that a shell is filled with a silicone gel having an appropriate viscosity. The silicone gel filled artificial breast prosthesis has superior product durability and a more pleasant texture than the saline filled artificial breast prosthesis and thus achieves a dominant position in the market. Although the Food and Drug Administration of the United States of America (FDA) has imposed limitations on use of silicone gel filled artificial breast prostheses due to safety issues, the use of silicone gel filled artificial breast prostheses was again allowed officially in 2006.
The silicone gel filled artificial breast prosthesis has been developed in the order of a first generation prosthesis, a second generation prosthesis, and a third generation prosthesis. This development history will be described in detail as follows.
The first generation silicone gel filled artificial breast prosthesis is a product sold from the middle of the 1960s to the middle of the 1970s, and was initially developed in 1961 by Cronin and Gerow. The first generation silicone gel filled artificial breast prosthesis can be represented in brief by the use of a thick shell, a smooth surface, and a high viscosity silicone gel. This prosthesis suffers from gel bleed and capsular contracture, but a rupture speed thereof is relatively low due to the use of the thick shell.
The second generation silicone gel filled artificial breast prosthesis is a product sold from the middle of the 1970s to the middle of the 1980s, and includes a thin shell and a silicone gel filling material of a low viscosity, for the sake of smoother texture. This prosthesis is characterized by a similar gel bleed rate, higher rupture occurrence, and lower capsular contracture as compared to the first generation prosthesis.
The third generation silicone gel filled artificial breast prosthesis is a product sold from the middle of the 1980s to the present, and includes a gel bleed barrier layer to prevent gel bleed. The third generation silicone gel filled artificial breast prosthesis includes a thicker shell and silicone gel of a higher viscosity as compared to the second generation prosthesis. In addition, a product having a rough surface has been developed, in order to reduce capsular contracture.
Such artificial breast prostheses commonly include a shell, a filling material, and a bonding portion (hereinafter referred to as a “patch bonding portion,” which is a common term in the art to describe a portion in which a hole generated during a process of detaching a shell from a mold is closed).
Shells are mostly manufactured via dipping and thus have limited durability (particularly, fatigue rupture is a risk). Basically, the shell produced via dipping has a thickness difference in upper and lower portions of the shell due to gravity, and this thickness difference causes a portion of the shell to be relatively weak to stress.
To increase shell durability in consideration of fatigue rupture, absolute strength of a shell can be increased to some extent by increasing an overall thickness of the shell. This also has limitations in that a lower end of the shell is very thick while increasing the overall thickness of the shell and thus flexibility of the breast prosthesis is deteriorated. For example, in the case of a shell having an average thickness of 1 mm or less, the thickness of a lower end portion thereof increases by about 1 mm as the thickness of an upper end portion thereof increases by 0.3 mm, which results in a greater thickness difference.
In addition, processing of a patch bonding portion is performed using a patch (a patch bonding material) and an adhesive material. In conventional fabrication of artificial breast prostheses, a patch used as a bonding material in the patch bonding portion has the same thickness and physical properties as those of the shell.
In this regard, to prevent deterioration of patch strength, the patch has to have a multilayer sheet structure including a leakage prevention layer formed of low molecular weight silicone inside the patch. However, it is very difficult to industrially and technically fabricate a patch in the form of a thin film including the leakage prevention layer therein and having a smaller thickness than the shell. Thus, a portion taken by cutting a shell is commonly used as the patch in the art.
That is, as illustrated in FIG. 1(a), a conventional breast prosthesis uses a patch 6 having the same thickness as that of the thickness (an average thickness of 0.5 to 1 mm) of a silicone shell (portions 5 and 7) and thus the thickness of patch bonding portions 8a and 8b, in which portions of the patch 6 and the silicone shell overlap each other, significantly increases and elongation characteristics of the patch bonding portions are very poor. In addition, in the case of a conventional breast prosthesis illustrated in FIG. 1(b), a central portion of a patch bonding portion is thinner than peripheral portions thereof and thus stress concentration occurs due to differences in physical properties at a boundary portion between the portion 7 of the silicon shell and each of the patch bonding portions 8a and 8b and, accordingly, problems in terms of resistance to fatigue of the patch 6 occur. Due to this, clinical studies have shown that rupture around a patch of an artificial breast prosthesis very frequently occurs.
U.S. Pat. No. 6,074,421 as the related art for such patch bonding portions discloses a patch bonding portion of a seamless artificial breast prosthesis. The present application relates to patch bonding technology for a patch bonding portion having the structure illustrated in FIG. 1(b) and discloses an artificial breast prosthesis in which a shell 7 has inclined edges at a hole thereof in an adhesion region between the patch 6 and the shell 7 and thus there is no seam-line formed between the patch 6 and the shell 7, whereby the artificial breast prosthesis has beautiful exterior appearance.
However, the above-described related art focuses only on improvement in terms of exterior appearance of the artificial breast prosthesis and does not consider improvement in overall performance, including durability, of the artificial breast prosthesis. Thus, the artificial breast prosthesis has a beautiful overall exterior appearance, while it uses a patch having the same thickness as that of the shell and thus the patch bonding portion is partially very thick and a central portion thereof is thin and, accordingly, there are differences in elongation and tension properties between each of the patch bonding portions and the silicone shell and stress concentration occurs due to differences in physical properties at a boundary portion between the shell and each of the patch bonding portions, resulting in deteriorated resistance to fatigue, which is the same problem as that of other existing artificial breast prosthesis fabrication technologies.
In addition, EP 0872221A1 as another related art similar to the above-described related art discloses patch bonding portions of a seamless artificial breast prosthesis and basically discloses the technical feature illustrated in FIG. 1(b) and further discloses an artificial breast prosthesis patch bonding technology characterized by a feature illustrated in FIG. 2(a). The present related art discloses an artificial breast prosthesis manufactured by forming a layer as illustrated in FIG. 2 at an outer side of a shell 7 in the vicinity of a hole to be closed by a patch 6 and bonding the patch 6 thereto and thus there are no seam-lines at bonding portions of the shell 7 and the patch 6, whereby the artificial breast prosthesis has a beautiful exterior appearance.
In this regard, although the patch bonding portions as illustrated in FIG. 1, i.e., overlapping portions 8a and 8b between the shell 7 and the patch 6, are not formed at an outside of the shell 7, as illustrated in FIG. 2(a), a central portion of the patch 6 has a smaller thickness than that of the patch bonding portions as in the aforementioned related art and thus stress concentration occurs at boundary portions of the patch bonding portions due to difference in physical properties between each patch bonding portion and the silicone shell, resulting in deteriorated resistance to fatigue, which is the same problem as that of other existing artificial breast prosthesis fabrication technologies.
In addition, as illustrated in FIG. 2(a), there is a hole with a tilted cross-section formed at an outer side of the shell 7 and bonding between the shell 7 and the patch 6 is not satisfactorily formed due to the hole and thus, in fact, seam-lines between the shell 7 and the patch 6 are formed, which makes it difficult for the present related art to achieve technical goals thereof.
In addition, as illustrated in FIG. 2(b), directions of pressure applied to a patch adhesion portion disposed at a rear surface of an artificial breast prosthesis in accordance with main pressure applied to the artificial breast prosthesis by motion or movement of a user after insertion into the human body are represented by arrows illustrated in FIGS. 2(a) and 2(b).
The above-described adhesion structure has a structure in which a hole of a shell is closed from the outside and, as illustrated in FIG. 2, when compared to an artificial breast prosthesis, a hole of which is closed from inside, in terms of pressure applied to the prosthesis, the patch adhesion structure is easily detached mechanically. In addition, in the above-described adhesion structure, pressure applied to the artificial breast prosthesis according to movement of a user after surgical implantation is concentrated in a narrower area than pressure applied to the patch adhesion portion, and thus, the adhesion structure has poor durability when compared to a patch adhesion structure that disperses pressure over a wider area, such as a structure in which a hole of a shell is closed from the inside. Thus, it is obvious that a structure in which a layer or a step is disposed at the inside of the shell and a patch is adhered thereto has mechanical and physical resistance to pressure applied to the artificial breast prosthesis after surgical implantation and excellent adhesion durability.
However, it is very difficult to adhere a patch to a shell provided thereat with a layer or a step with no gap therebetween from technical and industrial perspectives. This is because technology for forming a layer or a step at the inside of the shell and adhering a patch to the shell with no gap therebetween is incomparably difficult in terms of degree of difficulty, when compared to the above-described technology for forming a layer or a step at the outside of a shell and adhering a patch to the shell with no gap therebetween.
In addition, the aforementioned related arts are limited only in terms of exterior appearance improvement of products, not considering technical solutions in terms of physical characteristics and durability of a product and each element thereof. Thus, the above-described related arts do not technically consider pressure applied to the adhesion structures according to movement of a user after surgical implantation, adhesion durability against pressure, and overall durability of the artificial breast prostheses.
In addition, conventionally, as in the enlarged region illustrated in FIG. 2(a), a gap or crack 12 is generated at an adhesion boundary point 13 of the adhesion portion between the shell 7 and the patch 6.
This is because, in the related art or currently-used technologies, liquid silicone rubber (LSR) or silicone gum with little fluidity and having a very high viscosity has to be used as a bonding material 11 used in a process of adhering an already-hardened silicone shell to an already-hardened patch with a certain thickness. In other words, in a process of completely adhering the patch to a layer or step with angled edges formed at the silicone shell, a bonding material or adhesive 11, such as LSR or silicone gum having high viscosity, is not coated on side surfaces of the patch and only a lower end portion thereof is coated such that side surfaces of the shell and the patch are not adhered to each other.
It is obvious that such gap or crack deteriorates durability of an artificial breast prosthesis which is subjected to substantial stress and fatigue over time after surgical implantation.
The adhesion structures of the aforementioned related arts focus only on exterior appearance improvement of artificial breast prostheses and do not consider improvement in physical properties including adhesion durability and overall durability of the prostheses.
In addition, a filling material is injected into the inner space of a shell using a needle of a separate syringe device, and the needle is removed after injection of the filling material is completed. In this regard, a fine hole (hereinafter referred to as an “inlet”) is formed after removal of the needle. Conventionally, as illustrated in FIG. 3(a), leakage of a filling material is prevented by sealing a lower portion of a patch 6 at which an inlet 3 is formed using silicone 4 for sealing, such as a silicone solution, silicone gum, or the like so as to prevent the filling material from leaking via the inlet 3 formed after injection of the filling material, or, as illustrated in FIG. 3(b), first, a frame 2 having a ring shape is prepared, a central portion thereof is perforated using a needle so as to allow the filling material to be injected therethrough, the inlet 3 is sealed by silicone 4 for sealing, such as a silicone solution, silicone gum, or the like after injection of the filling material to prevent the filling material injected into the shell from leaking to the outside.
However, when a conventional structure and fabrication method for sealing the inlet 3 is used, the silicone 4 for sealing applied to seal the inlet 3 and edges thereof are exposed to the outside and thus provide poor exterior appearance, and the silicone 4 and the edges thereof rub against the outside and thus may be easily detached.
Such phenomenon frequently occurs when a filling material used for injection sticks in a region to be coated with the silicone 4 or to which the silicone 4 is to be applied. Such phenomenon almost inevitably occurs in filling and hardening processes in manufacture of an artificial breast prosthesis, which is addressed using a method of sealing the inlet 3 after wiping leaked filling material off of the inlet 3. However, the inlet 3 is sealed with the filling material leaked due to operator carelessness such as incomplete wiping and thus the silicone 4 for sealing the inlet 3 may be easily detached.
As such, the filling material injected into the shell may leak to the outside and, accordingly, product quality and safety is significantly reduced.
To address these problems, Korean Patent Application Publication No. 10-2011-0041990 discloses prevention of leakage of a filling material by, as illustrated in FIG. 4(a), forming a filling material injection groove 9 having a concave shape, which is a space through which the filling material is injected into an inner space of a silicone shell using a needle, at a central portion of a lower surface of a patch part 6 and then sealing the filling material injection groove 9 using silicone 9a, such as a silicone solution, silicone gum, or the like after injection of the filling material. Due to such configuration, the silicone 9a used to seal an inlet and edges thereof are not exposed to the outside, whereby detachment of the silicone 9a due to external rubbing may be prevented as much as possible.
However, as described above, problems in terms of weak adhesive strength of an inlet sealing portion due to leakage of a filling material remain to be solved.